The ongoing WebmasterWorld thread has a nice uptick in chatter this weekend starting around Saturday but staying strong throughout Sunday on ranking changes and traffic changes.
It looks like the changes started later Friday when member, backdraft7, said:
Looks like somebody tripped on the network cable on our server again. NO traffic for long periods today. 20 and 30 minute periods of absolutely NOTHING! Well, at least it can't get any worse that zero? Can it? Come on what gives? I'm still in the serps, but ZERO? Did every on the planet die?
Several SEOs and webmasters also noticed major changes afterwards.
Another SEO added, "Traffic STOPPED completely 30 minutes or so ago. WOW is all I can say..."
Like all ranking fluctuations discussed in these threads, it doesn't mean there was a global update or anything. It can be site specific or even a bug with the site or Google.
One other Webmaster added:
We saw similar patterns yesterday. Not "zero" traffic, but huge drops in traffic at times during the day. Mostly in the afternoon as the morning started off normal (Central time zone). I kept checking the news to see if some disaster had struck that was taking everyone's attention away because like you, our SERPS hadn't changed so it made no sense.
Honestly, I don't think this will be a major update like anything Penguin or Panda related. But I'll stay on top of it.
Forum discussion at WebmasterWorld.